1. Technical Field
The present invention relates to an apparatus and method for low power local area communication using event signal control.
2. Description of the Related Art
ZigBee, one of Wireless Personal Area Network (WPAN) technologies, is a personal wireless network standard which is characterized by low power, low cost, and low data rate and which is required for 2.4 GHz-based home automation and data. Such ZigBee has been standardized in IEEE 802.15.4.
With reference to the standard, ZigBee uses 2.40 GHz, 915 MHz, and 868 MHZ frequency bands, and may have 250 kbps (16 channels in the 2.4 GHz Industrial, Scientific and Medical (ISM) bands) and 40 kbps/20 kbps (10 channels in the 915 MHz band/1 channel in the 868 MHz band) transmission rates for respective frequencies. The modem type of ZigBee is Direct Secure Spread Spectrum (DSSS), which enables data to be transmitted at 20 to 250 kbps data rates in a 30 m radius, and enables 255 devices to be connected to a single wireless network at most, so that a large-scale indoor/outdoor wireless sensor network can be constructed.
Compared with another WPAN technology such as Bluetooth or Ultra Wide Band (UWB) communication, ZigBee enables ultra-low power consumption to be realized and the construction of a wireless transmission/reception circuit to be simplified, so that there is an advantage in that the cheapest chipset price can be realized. ZigBee is a short range wireless communication technology which is competitive in the area of vertical applications such as a sensor network.
Such ZigBee has been utilized in various applications such as access control, location tracking, logistics management, and building management. For example, if ZigBee is introduced into lighting, fire sensing, air-conditioning and heating systems in a building, a building manager can remotely manage and control the building system using a portable device without staying in the janitor's office.
WPAN based on such ZigBee technology may include a single network coordinator and a plurality of network devices each of which is connected to the network coordinator and which transmits and receives data.
In the construction of such WPAN, the network coordinator is included in a computer or the main control device of a home network, and is configured to control data transmission and reception to and from the plurality of network devices. The network devices are parts for actually inputting and outputting data, and, in the case of home automation, may correspond to a heating system, a ventilation system, an air conditioner, a security system, a light, and a sensor.
In order to realize low-power characteristics in ZigBee, the network devices are operated in the state in which the receivers thereof are turned off for most of the time except for time required for synchronization.
In this case, the network coordinator transmits superframe beacons at predetermined time intervals. Here, the intervals between beacon signals may range from a minimum of 15 msec to a maximum of 245 msec. In order to reduce power consumption, each of the network devices is operated in the state in which it is turned off, aside from the case in which it receives periodic beacon signals.
Therefore, when a single coordinator simultaneously broadcasts packets to a plurality of network devices, there is a problem in that network devices which are turned off cannot completely receive the packets which have been broadcasted.
In order to solve the problem, a method of allowing a ZigBee system and a Radio-Frequency Identification (RFID) system to be installed together in a single module and to operate in conjunction with each other has recently been proposed.
In conventional ZigBee systems, a ZigBee system using an RFID is constructed in such a way that a network coordinator further includes an RFID reader and each of network devices includes an RFID tag. The system presents a method of enabling data transmission and reception between the network coordinator and the network device in such a way that the RFID reader transmits a signal to the RFID tag of the network device, and that the RFID tag transmits a wake-up signal to the ZigBee system of the device in response to the received signal, thereby waking up the ZigBee system from the state of being turned off.
However, such a system should operate two types of communication standards in such a way as to enable the ZigBee system and the RFID system to be installed in each of network communication modules. Accordingly, the construction of the system is complicated and requires high cost.
Further, since the network device needs a separate power, the network device generally uses an additional small-sized battery. An active type system which is used with a battery cannot be operated for a long time due to the limited capacity of the battery.
Furthermore, since such a method should operate two types of communication standards in such a way as to enable both the ZigBee and RFID systems to be installed in each of the network communication modules, the construction of the system is complicated. In addition, since an expensive RFID reader should be provided in the construction of the system, high cost is caused.